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Dinic求解释···TL了一个晚上。麻烦大神们指点下
#include <algorithm>
#include <iostream>
using namespace std;
#define MAX 20000
#define INF 9999999999999999
#define min(a,b) (a<b?a:b)
struct Edge
{
int st, ed;
__int64 flow;
int next;
} edge[MAX*3];
int head[MAX], out[MAX];
int stk[MAX], que[MAX];
int leve[MAX];
bool vis[MAX];
int E, src, sink;
inline void add_edge ( int u, int v, __int64 flw )
{
edge[E].st = u;
edge[E].ed = v;
edge[E].flow = flw;
edge[E].next = head[u];
head[u] = E++;
edge[E].ed = v;
edge[E].st = u;
edge[E].flow = 0;
edge[E].next = head[v];
head[v] = E++;
}
__int64 Dinic()
{
__int64 maxFlow = 0;
int front, rear, top;
int cur, u, i;
while ( 1 )
{
memset(leve,-1,sizeof(leve));
front = rear = leve[src] = 0;
que[rear++] = src;
while ( front != ( rear + 1 ) % MAX )
{
u = que[front];
front = ( front + 1 ) % MAX;
for ( i = head[u]; i != -1; i = edge[i].next)
{
if ( edge[i].flow && leve[edge[i].ed] == -1 )
{
leve[edge[i].ed] = leve[u] + 1;
que[rear]= edge[i].ed;
rear = ( rear + 1 ) % MAX;
}
}
}
if ( leve[sink] == -1 ) break;
for ( i = src; i <= sink; i++ ) out[i] = head[i];
top = 0;
while ( 1 )
{
if ( top == 0 )
{
for ( cur = out[src]; cur != -1; cur = edge[cur].next )
if ( edge[cur].flow && out[edge[cur].ed] != -1 && leve[edge[cur].ed] == 1 )
break;
if ( cur < 0 ) break;
stk[top++] = cur;
out[src] = edge[cur].next;
}
u = edge[stk[top-1]].ed;
if ( u == sink )
{
__int64 dd = INF;
int index = -1;
for ( i = top - 1; i >= 0; i-- )
{
if ( dd >= edge[stk[i]].flow )
{
dd = edge[stk[i]].flow;
index = i;
}
}
maxFlow += dd;
for ( i = 0; i < top; i++ )
{
edge[stk[i]].flow -= dd;
edge[stk[i]^1].flow += dd;
}
top = index;
}
else
{
for( cur = out[u]; cur != -1; cur = edge[cur].next )
if ( edge[cur].flow && out[edge[cur].ed] != -1 && leve[u] + 1 == leve[edge[cur].ed] )
break;
if ( cur != -1 )
{
stk[top++] = cur;
out[u] = edge[cur].next;
}
else
{
out[u] = -1;
top--;
}
}
}
}
return maxFlow;
}
int dfs ( int u )
{
vis[u] = true;
int v, i, cnt = 1;
for ( i = head[u]; i != -1; i = edge[i].next )
{
v = edge[i].ed;
if ( ! vis[v] && edge[i].flow > 0 )
cnt += dfs(v);
}
return cnt;
}
int main()
{
__int64 sum = 0;
int n, m, u, v, b;
scanf("%d%d",&n,&m);
E = src = 0;
sink = n + 1;
memset(head,-1,sizeof(head));
for ( int i = 1; i <= n; i++ )
{
scanf("%d",&b);
if ( b > 0 )
{
sum += b;
add_edge ( src, i, b );
}
else add_edge ( i, sink, -b );
}
while ( m-- )
{
scanf("%d%d",&u,&v);
add_edge ( u, v, INF );
}
memset(vis,0,sizeof(vis));
__int64 maxFlow = Dinic();
int cnt = dfs ( src ) - 1;
printf("%d %I64d\n", cnt, sum - maxFlow);
return 0;
}
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